1. Field of the Invention
The invention relates in general to a projection device with a color wheel locking function and a method using the same, and more particularly to a device and a method thereof, in which an external magnetic force is provided to lock a spindle motor therein so that a color wheel is locked at a specified position.
2. Description of the Related Art
Most people have the experience of using projectors in conducting either the presentations, conferences or speeches in the occasions of company and seminars, or the video playback in the general family. The applications in conjunction with projectors can provide the viewer excellent presentation and visual effects by way of large-screen projection display.
Generally speaking, the projector uses a color wheel to process a white light beam, generated by a light source and illuminated thereon, into corresponding color light beams for projection. The color wheel is a disk rotatable at a high speed, and has light filtering regions of different colors, wherein the colors usually include red, green and blue colors. That is, the three primary colors of RGB are arranged on the color wheel. By controlling the rotational speed of the disk, different color light beams can be rapidly and continuously emitted. In addition, multiple colors of an image can be generated and presented according to the persistence of vision phenomenon of the human eye.
In addition, to emphasize different applications and projection effects of the projector, different color arrangements on the color wheels may be designed. For example, in the application where the luminance is particularly emphasized, a white or transparent region can be added to the color wheel, so that the light beam illuminating the white or transparent region projects as a color-free light beam. Alternatively, the color wheel is directly designed to have a notch, so that most of the light beams of the light source can transmit through the notch, and the better effects on the presentation of the luminance of the image are obtained.
Alternatively, another color or other colors other than the three primary colors can be added in order to achieve a special color projection effect. However, no matter which application is required, the sizes and the ratios of the regions occupied by various colors are adjusted according to the divided graduations on the disk so as to adjust illuminated time periods of different colors and thus to change the feeling of the human eyes seeing the color of the projected image.
Therefore, in order to achieve the functions of emphasizing the image luminance and color property, the prior art is to dispose two color wheels inside the projector. That is, one color wheel has a notched transparent region, and the other color wheel is an integral disk composed of non-transparent regions.
FIG. 1A is a schematic view showing an inner structure of a conventional projector 100 having two color wheels. As shown in the drawing, original positions of a first color wheel 12 and a second color wheel 14 partially overlap with each other on an optical path 101 of a light beam generated by a light source 10. The two color wheels 12 and 14 can be rotated by the spindle motors 11 and 13, respectively, and the generated light beam can be reflected at various angles through a data plane 15 (may be a reflective DMD) to project the image been seen. The overlapping of the two color wheels 12 and 14 is depicted in FIG. 1B.
As mentioned hereinabove, one of the color wheels needs to have a mechanical moving function in the projector with two color wheels. As shown in FIGS. 1A and 1B, the first color wheel 12 has a transparent region 120. When the second color wheel 14 needs to operate, the first color wheel 12 is rotated so that its transparent region 120 is disposed on the optical path 101, and the light beam of the light source 10 can illuminate the second color wheel 14 and transmit through the transparent region 120 without being affected. The second color wheel 14 is designed to have the relative moving structure. When the first color wheel 12 needs to operate, the second color wheel 14 can be moved away from the optical path 101 to avoid interfering with the illuminating light beam.
In other words, if the two color wheels are designed to be movable, then the interference between the two color wheels can be effectively avoided. However, such a design inevitably increases the manufacturing cost and the overall size of the device. Thus, it is an important development direction of such the projector to ensure that each color wheel can be moved to or locked at the correct position under the precondition that only one color wheel is movable.